In elevators known to the art, the elevator car, traveling up and down in a hoistway, is controlled by a car controller, typically located in a machine room at the head of the hoistway, along with the sheave, motor and brake which control the motion of the car. In most elevators known to the art, the car is literally a slave to the car controller, the car controller telling the car when to open and close its doors, and otherwise performing essentially all the functions necessary to raise and lower the car into position accurately at landings. Even in the case of apparatus mounted on the car itself, the apparatus is simply directly wired through the traveling cable to the car controller, and the analysis of conditions represented by the signals in the wires is performed by the car controller.
In the case of conditions relating to the car which are sensed or created at the car itself, a safer degree of operation would result if the car were able to analyze such conditions, and contribute in the control of the functioning of the car as a consequence of conditions, particular those that relate to passenger safety.
In systems known to the art, the car controller would not only control the functions performed within the car itself, but would receive signals which it would then analyze to determine whether the car response ultimately seemed to be proper or not. For instance, only the car controller was cognizant of such dangerous conditions as the elevator door not being fully closed when the elevator was located away from the landing or when the car was traveling at excessive speed. And the response of the car controller to any such condition simply had to be the sending of a command to the car, whether it could be acted on or not, to try and correct the condition (such as a force doors closed command). Or, the car controller could arrest the motion of the car if it determined such a case to be warranted.